TFL, or transcription factor one, is a protein isolated from SPOl virus infected B. subtilis which has the properties of a DNA template-specific inhibitor of transcription. We propose to: 1) Study the conformation and protomer interactions of TFL in solution. 2) Study TFl-DNA interaction. Such studies will include the stoichiometry and equilibria as a function of ionic strength, temperature and metal ion concentration. The effect of TFl on RNA polymerase binding to DNA will be investigated. 3) Study of the effect of chemical modification of TFl on its binding to DNA. 4) Auxiliary studies of TFl synthesis by bacteria infected with various viral mutants and of TFl in mature virus will be undertaken.